1. Field of the Invention
This invention pertains generally to action mechanisms of a piano, and more particularly to an improved keyboard action with low friction, corrosion resistant anodized aluminum key pins and action guide pins.
2. Description of Related Art
The finest pianos provide a uniform “feel” when the keys are depressed by the musician as the instrument is played. Force, applied to a key by the pianist, is transmitted through a repetition assembly and a hammer shank accelerating a hammer made from wood and felt. Traveling very rapidly, the hammer strikes a set of strings causing them to vibrate. As the strings vibrate, they shake the soundboard which in turn causes the ambient air to vibrate. It is this vibration in the air that is perceived as sound, or music, from the piano. The volume and tonal quality of the sound that is produced by the strings depends on force applied to the key by the musician and the interaction of the large number of moving parts that constitute the “action” of the piano.
A uniform feel for each key, with the right amount of resistance, permits the musician to have control over the volume of the music and to play expressively. It is important that the applied force that is required to depress each key to be similar to provide an even overall feel. In a piano, volume and tone change as function of the speed of the hammer as it hits the string. A pianist is able to control this by varying the force applied to each key. If the force required is significantly different from key to key, then it becomes difficult to control the sounds made by the piano. The ability to vary the volume and tone of a musical note by controlling the speed of the hammer striking the strings is central to the skill of a pianist. It is in this fashion that a skilled performer can play a wide variety of compositions. Some pieces require quick, sharp combinations of notes; others utilize softer more gentle legato combinations. The pianist depends on the action to be in control of his own artistic vision.
The overall “touch” or “feel” of the keyboard of an acoustic piano is the result of the weight of the parts of the action and the resistance from friction between the moving parts of the components of the action. Precision machining and good quality control allow piano manufacturers to make piano actions that have uniform weights and tight tolerances. However, friction that occurs between the components of the action of the piano can be unpredictable and difficult to control.
Action centers are the pivotal connections between components of the action around which the various parts rotate. As with any shaft and bearing system, there must be limited side to side movement, while the parts rotate smoothly with minimal friction. Components of these action centers are typically held together with a lateral or transverse pin with suitable bushings. In the case of piano actions this bushing material is a dense woven cloth called bushing cloth.
With a piano key, the key pins and bushings are not a shaft and bearing system. Rather, the key pins and associated bushings guide the motion of the key as it rotates on a balance hole in the bottom of the body of the key. The resistance caused by the key bushings rubbing on guide pins is undesirable because this resistance slows the movement of the keys and adds directly to the effort that the pianist must expend to play the piano.
Action center pins are conventionally made of brass with a nickel coating. The purpose of the nickel coating is to decrease the friction between the cloth bushing and the pin. Because the pin is not particularly open to the air, corrosion is less of a problem than heat created in the bushing as the piano is played. Heat can be a significant problem because it can cause the cloth bushing to swell and cause the action center to seize up or greatly increase in friction. Anything that can reduce the friction in the action pins is significant and valuable in the manufacture of pianos.
Key pins, the guide pins of the key, are typically made of brass or soft steel with thin coating of nickel. Like the action center pins, the purpose of the nickel coating on the key pins is to decrease the friction between the cloth bushing and the pin. Because the key pin is exposed to the atmosphere, corrosion can be a significant problem particularly in a high humidity environment. Corrosion can greatly increase the friction between the key and the keypin. Correcting this condition requires disassembly of the keyboard to provide access to the corroded parts. Polishing key pins is laborious, time consuming and the results are temporary. Attempts to apply coatings of other metals such as chrome to the key pins have been unsuccessful. Such coatings have either not resisted corrosion or have frictional coefficients that are too high resulting in a sluggish or heavy action.
Durability of the conventional key pins and bushings exposed to repetitive motion has been limited due to the soft nature of the surface coating as well as corrosion. As corrosion adds friction, excessive wear on the cloth bushings that guide the key can occur. Worn key bushings cause the key to move from side to side in a loose and uncontrolled fashion. Added friction can also lead to sticking keys. While the key pins are capable of replacement, key pins are not normally replaced because it is an expensive, time consuming and laborious task.
There have been many attempts to improve the design of piano actions and bearings to reduce friction in the action centers and to increase the longevity of the parts. Bushings of various materials other than traditional wool felt have been proposed, some with lubricants such as graphite, silicone or soap. However, such materials do not eliminate the problem of corrosion or increase the durability of the action pins that typically lose lubricity over time.
Alternative action designs with additional moving parts and action points have also been developed. Such designs are still vulnerable to corrosion in humid environments and to limited durability during long use.
Accordingly, there is a need for a piano action using low friction action pins and key pins that exhibit low friction and extended durability over the lifetime of the piano. The present invention satisfies these needs, as well as others, and is generally an improvement over the art.